1. Field of the Invention
This invention relates to a nonskid device, more particularly to a nonskid device incorporated in, for example, a vehicle tire for preventing the vehicle from slipping when traveling over an icy or snowy surface.
2. Prior Art Statement
In Japan, snow tires having treads provided with numerous studs are commonly used to prevent vehicles from slipping on icy surfaces. The tread of such a snow tire has embedded therein numerous studs which project from the tire surface by 1.5 to 2.0 mm. The studs are ordinarily provided with hard metal tips to protect them from wearing down. When a vehicle fitted with such studded snow tires travles over a road surface that is not covered with ice or snow, the road surface is gouged by the hard metal tips of the studs, and the gouged out material enters the surrounding air in the form of dust. This produces a pollution problem. One countermeasure that has been tried for holding down the amount of dust kicked up by vehicles using studded tires is that of limiting the projecting length of the studs to 1.0 to 1.5 mm and reducing the number thereof from the conventional 154 per tire to 122 per tire. While this is of course helpful, it is by no means a fundamental solution to the problem. What is more, it reduces the performance of the tire on icy surfaces and thus gives rise to a safety problem.
With a similar aim, there have also recently been proposed devices which project and retract studs depending on the road surface condition. The studs of these devices are, however, extremely complex in structure, and since they require a source of power (for example, a pneumatic or electrical actuator) for projecting and retracting the studs, they tend to be large in size and high in cost. This has prevented their practical application.
Therefore, there is a need for a nonskid device which does not gouge the road surface, is capable of maintaining the performance of the tire on snow and ice covered surfaces and thus ensuring safe travel over such surfaces, does not produce air polluting dust when traveling over a road surface not covered with ice or snow, and is small in size, low in cost, and reliable in operation.